(1) Field of the Invention
The present invention relates to a tilter for a Venetian blind, particularly a tilter mechanism to directly rotate a headrail of the Venetian blind.
(2) Description of the Prior Art
Venetian blinds are composed of a plurality of vertical or horizontal slats running in parallel, tilting of which can adjust indoor darkness and preserve privacy. They are. It is being extensively used in offices and homes. The conventional horizontal Venetian blind being used can have its slats tilted and lifted, and comprises mainly a rectangular sectioned and non-rotary headrail, a foot rail, two or more ladders each including an outer ladder and an inner ladder suspend from the headrail to the foot rail to support a plurality of slats with a plurality of connecting tapes located between the outer and inner ladders, and a tilter within the headrail and a transmission device therefor to tilt the slats. The tilter and the transmission device are incorporated with a handle to tilt the slats manually, and are substantially in a form of the drum driven by a worm drive through the handle for rotation, include at least two tilt drums each wound by a ladder to support the ladder, and a transmission shaft located between the tilt drums to rotate the tilt drums simultaneously. When the handle is operated, the ladders are moved linearly by the tilter, transmission shaft and the tilt drums, the outer and inner ladders are moved in two opposite directions to tilt the slats between them.
The conventional tilter for Venetian blind is firmly secured to a headrail, and has a worm drive and a plurality of transmission shafts to rotate the respective ladder drums suspending the slats. Such a tilter has a quite complicated structure, and hence, its production cost is high. Moreover, it is hard to implement mass production with an automatic assembly process, and it has the following defects:
(1) In general a ladder drum is located near each end of the headrail to maintain a good balance for the slats, but a transmission shaft having a length nearly equal to the length of the headrail must be provided between the ladder drums, and a plurality of bearings must be placed to support such a long transmission shaft, hence, the overall weight of the Venetian blind is significantly increased, the long transmission shaft means a relatively long momentum arm, and a considerable large force is required to rotate the ladder drums simultaneously for tilting the slats to a desired angle.
(2) Such sophisticated tilter requires assembly at a factory, and its installation position can not be changed after it is assembled to satisfy the user's personal taste or environmental requirements. Production and use of such tilters are inconvenient.
(3) The worm drive, bearing and gears in the conventional tilter will lose its transmission efficiency due to improper use, prolonged exposure to dusts and other factors which damage proper engagement among its components.